The human body is comprised of various organs that generate, or are subject to, a variety of pressures. These pressures are primarily induced externally due to gravity and include atmospheric compression and body weight opposition. However, there are also a wide range of pressures produced within the body itself. These pressures include those generated by the cardiovascular system, urinary system, digestive tract, musculoskeletal system, central nervous system, osmotic cell pressures, among others. Most of these pressures are critical for proper health and must be precisely regulated. Blood pressure of the cardiovascular system and cerebral spinal fluid (CSF) of the central nervous system are two such components that must be precisely maintained. The ability to continuously monitor these pressures would allow for early detection and intervention in the event auto-regulation becomes impaired.
Intracranial pressure is among the most critical found within the body whereby intracranial hypotension, resulting in brain matter migration, can lead to ruptured blood vessels along the surface of the brain and hematomas while CSF hypertension can lead to decreased blood perfusion within the brain. Either case can quickly become life-threatening and is estimated to affect one to two percent of the population congenitally by hydrocephalus, or acquired due to brain tumor, traumatic obstruction, or damage to the arachnoid villi from meningitis, for example.
Long term monitoring of intracranial pressures (ICP) induced by CSF is of particular interest since chronic elevated ICP is common in patients with hydrocephalus and can become life-threatening in acute cases or when shunt treatments fail or if left untreated. However, current state of the art monitoring devices require sensors to be placed within the brain and tethered to bedside equipment in order to measure the pressure. Such measurements typically only allow ICP monitoring for days at a time, due to both the required invasiveness and also due to sensor drift, and require an acute care clinic setting to facilitate these complicated and risky measurements. Patient position becomes critical for accurate measurements by these systems and since the sensor is percutaneously tethered from within the brain to a bedside instrument, the risk of infection is high. What is needed is a self-contained long-term implantable bio-pressure sensor transponder to facilitate recurring and extended in-vivo CSF pressure measurement assessments non-invasively, ex-vivo, and which can be routinely calibrated for accurate long-term assessment thereby overcoming sensor drift errors and limitations.